A. Field of the Invention
The present invention relates most generally to the field of heating and serving systems and more particularly to an improved tray which is inserted into an electromagnetic heating system which selectively heats various elements of a load, such as a complete meal or the like, in a single operation.
B. DESCRIPTION OF THE PRIOR ART
In institutions, such as hospitals, it is desirable to provide a system whereby a complete meal may be brought up to serving temperature in a single, quick operation. If this can be done, the meals may be prepared in an assembly line fashion on week days during normal working hours and then they may be kept refrigerated until the time when they are to be served.
A typical meal normally includes some food items which require heating before they may be served and other food items which are preferably served cold. For example, the salad and dessert portions of a meal are preferably served cold. The main entree of a meal is preferably served hot. If a meal includes coffee or tea, the coffee or tea is preferably served very hot.
A conventional oven ordinarily supplies heat energy to every portion of the meal. In an electromagnetic oven, on the other hand, any food item that is completely enclosed in an electrically conductive wrapper or shield is not heated. It is, therefore, possible to heat a complete meal in a microwave oven without heating, for example, a desert such as ice cream that is wrapped in aluminum foil or otherwise shielded. However, wrapping all items such as deserts, salads and beverages such as milk, in foil adds considerably to the cost of preparing a meal. Difficulties may also arise any time a shielded item is placed into an electromagnetic oven, because the shield distorts the electromagnetic field within the oven. Arcing can also result, especially if the shielding has any sharp edges or is positioned adjacent a conductive wall of the oven chamber. An electromagnetic oven heating system and shield for accomplishing the above described meal preparation system are described in U.S. Pats. No. 3,854,021 which issued to Donald G. Moore, et al. on Dec. 10, 1974 and 3,854,022 which issued to Donald G. Moore on Dec. 10, 1974. These patents are hereby incorporated by reference for all purposes and reference can be made to these patents for a more complete description of the background of the present invention.
In some applications, the level of microwave energy in the vicinity of the sensing device may be relatively low and more efficient coupling of energy to the sensing device is required in order that the sensing device reach its Curie point by the time the food items on the tray reach their desired serving temperatures.
Further, a tray that facilitates handling, as in insertion and removal from storage racks when serving the meals, is also required to insure the efficiency of the overall institutional feeding plan. Clearance or height problems in storage racks due to tilting and tall objects on the trays causes inefficiency and loss of food. Existing trays fabricated from some materials also allow an undersirable rise in temperature in the shielded areas that detracts from the overall optimization of the feeding plan and appeal of the meals.